B2B Energy Monitoring with Chassis Ground

[chicagoandy]

Hello,

I am looking to monitor the energy generation from my B2B system. I was assuming I could do this with a SmartShunt. However, these can only be attached to negative lines.

My van uses a Chassis Ground. The Lynx Distributor grounds the negative busbar to the chassis, and likewise the Ford batteries are grounded to chassis. As a result, on the B2B line I have not placed a Negative line. Since there is no negative line, how do I add a smartshunt?

The best option I've determined is to place the Shunt between the Lynx distributor and chassis. However, this connection is also a safety ground.

Are there better approaches to monitoring the B2B energy flows?

Goals:
1. Accurate energy monitoring of the B2B circuit on Cerbo GX.
2. Not intermixing the B2B with other DC loads.

 

[HarryN]

The shunt is a precision resistor of a very low value. There needs to be at least some voltage drop through it to work.

Think of your battery ( - ) terminal is being at the same voltage as the van official ground point. So one way to connect it up is to have both batteries and the van ground point all attached together at a bus bar that for conversation we can call ( Battery - )

The other items in the van ( loads, 120 vac, sterling and solar chargers ) are sort of on a "floating negative" bus bar.

These two bus bars are attached to each other with the shunt as the pathway to measure the current flow in and out of the battery pack.

If you want specific, dedicated monitoring of the sterling operation, just put an additional shunt into sterling ground path.

I don't know if the cerbo can provide info on it or not, but the info is there.

Simarine makes a monitoring system that can monitor all kinds of stuff like water tank levels, multiple shunts, etc. One of the local Sprinter owners / buddy wanted it in his van and we installed it without any serious issues. There was one component that he ended up ordering the wrong one but the company was very helpful so it wasn't an issue, just a time delay.

 

[chicagoandy]

If you want specific, dedicated monitoring of the sterling operation, just put an additional shunt into sterling ground path.

I guess this is the root of my question: What is the sterling ground path with a Chassis ground?

Is the charge flowing:
Lynx Distributor Negative Bus Bar - > Chassis Ground - > Sterling B2B - > Chassis Ground - > Ford Battery Negative?
Or are they going to skip the B2b entirely, and just go
Lynx Distributor Negative Bus Bar - > Chassis Ground - > Ford Battery Negative?

I suspect the second one. The Sterling has a non-isolated negative. I can't see why the charge would be motivated to come off the chassis, then go into the sterling... then back out the same connection on the way to the Ford battery. I guess I can test this once I get it setup, but my assumption is the non-isolated negative on the sterling will really only see enough current to power the Sterling circuitry, and the rest of the negative charge will flow directly to the Ford battery negative bypassing the sterling altogether.

Thus the only place to put a shunt is between the Lynx Distributor and Chassis Ground.

 

[HarryN]

I guess this is the root of my question: What is the sterling ground path with a Chassis ground?

Is the charge flowing:
Lynx Distributor Negative Bus Bar - > Chassis Ground - > Sterling B2B - > Chassis Ground - > Ford Battery Negative?
Or are they going to skip the B2b entirely, and just go
Lynx Distributor Negative Bus Bar - > Chassis Ground - > Ford Battery Negative?

I suspect the second one. The Sterling has a non-isolated negative. I can't see why the charge would be motivated to come off the chassis, then go into the sterling... then back out the same connection on the way to the Ford battery. I guess I can test this once I get it setup, but my assumption is the non-isolated negative on the sterling will really only see enough current to power the Sterling circuitry, and the rest of the negative charge will flow directly to the Ford battery negative bypassing the sterling altogether.

Thus the only place to put a shunt is between the Lynx Distributor and Chassis Ground.

The good news is that the wire is cheap, so you can proto it up and it will make more sense.